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1
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A diadenosine 5',5''-P1P4 tetraphosphate (Ap4A) hydrolase from Arabidopsis thaliana that is activated preferentially by Mn2+ ions

100%
Szurmak B., Wysłouch-Cieszyńska A., Wszelaka-Rylik M., Bal W., Dobrzańska M.
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2008
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vol. 55
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issue 1
151-160
EN
Asymmetrical diadenosine 5',5''-P1P4 tetraphosphate (Ap4A) hydrolases are key enzymes controlling the in vivo concentration of Ap4A - an important signaling molecule involved in regulation of DNA replication and repair, signaling in stress response and apoptosis. Sequence homologies indicate that the genome of the model plant Arabidopsis thaliana contains at least three open reading frames encoding presumptive Ap4A hydrolases: At1g30110, At3g10620, and At5g06340. In this work we present efficient overexpression and detailed biochemical characteristics of the AtNUDX25 protein encoded by the At1g30110 gene. Aided by the determination of the binding constants of Mn(Ap4A) and Mg(Ap4A) complexes using isothermal titration calorimetry (ITC) we show that AtNUDX25 preferentially hydrolyzes Ap4A in the form of a Mn2+ complex.
2
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Plant Metallothioneins: Putative Functions Identified by Promoter Analysis in Silico

88%
Dąbrowska G.
Acta Biologica Cracoviensia s. Botanica
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2012
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vol. 54
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issue 2
3
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Abscisic acid does not influence the subcellular distribution of the HYL1 protein from Arabidopsis thaliana

88%
Lesicka-Górecka J., Szarzyńska B., Sawczak M., Bagdiul I., Górski P., Jarmołowski A., Szweykowska-Kulińska Z.
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2008
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vol. 55
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issue 3
517-524
EN
HYL1 is a nuclear protein involved in the processing of miRNAs but its exact function remains unknown. Arabidopsis thaliana hyl1 mutants exhibit hypersensitivity to ABA. We decided to answer the question whether ABA affects the HYL1 protein localization within the cell and show that it does not. We also studied the expression of HYL1 in different tissues and organs. In this paper we show for the first time the expression profile of the HYL1 protein using anti-HYL1 antibodies. The protein is present in seedlings and mature plants in all organs studied, with the highest amount in inflorescences. A. thaliana HYL1 protein has several repetitions of a 28-amino-acid sequence at the C-terminus that confer protein instability. Our bioinformatic analysis of HYL1 homologs in different Brassica species shows that this repetition is typical only for Arabidopsis. This may suggest a relatively late evolutionary acquisition of the C-terminal domain.
4
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Biochemical characteristics of AtFAR2, a fatty acid reductase from Arabidopsis thaliana that reduces fatty acyl-CoA and -ACP substrates into fatty alcohols

88%
Doan T., Carlsson A., Stymne S., Hofvander P.
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EN
Fatty alcohols and derivatives are important for proper deposition of a functional pollen wall. Mutations in specific genes encoding fatty acid reductases (FAR) responsible for fatty alcohol production cause abnormal development of pollen. A disrupted AtFAR2 (MS2) gene in Arabidopsis thaliana results in pollen developing an abnormal exine layer and a reduced fertility phenotype. AtFAR2 has been shown to be targeted to chloroplasts and in a purified form to be specific for acyl-ACP substrates. Here, we present data on the in vitro and in planta characterizations of AtFAR2 from A. thaliana and show that this enzyme has the ability to use both, C16:0-ACP and C16:0-CoA, as substrates to produce C16:0-alcohol. Our results further show that AtFAR2 is highly similar in properties and substrate specificity to AtFAR6 for which in vitro data has been published, and which is also a chloroplast localized enzyme. This suggests that although AtFAR2 is the major enzyme responsible for exine layer functionality, AtFAR6 might provide functional redundancy to AtFAR2.
5
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Effect of Medicago sativa Mhb1gene expression on defense response of Arabidopsis thaliana plants

75%
Maassen A., Hennig J.
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2011
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vol. 58
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issue 3
427-432
EN
Besides the previously described nitric oxide-detoxification activity we identified new features of class-1 non-symbiotic hemoglobin from Medicago sativa (Mhb1). Under in vitro conditions, using peroxidase in-gel activity assay, the Mhb1 protein was shown to possess also peroxidase-like activity. Due to this activity, in the presence of nitrite and hydrogen peroxide, the protein can mediate autonitration and nitration of other proteins at tyrosine residues, as revealed by tandem mass spectrometry and immune assay approaches. Mhb1 through its multifunctional activities can affect different components of signal transduction cascades operating during plant response to infections. This influence is manifested by Mhb1-mediated selective up-regulation of expression of certain pathogen inducible genes in Pseudomonas syringae infected Arabidopsis thaliana plants which overproduce Mhb1, as revealed by reverse transcription-quantitative real-time PCR analysis. Changes in expression level of these genes can influence such processes as synthesis of secondary metabolites, protein degradation and biosynthesis of ethylene. They can also result in alteration of pathogen-induced defense response of Mhb1 transgenic plants.
6
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Photoinduction of Seed Germination in Arabidopsis Thaliana is Modulated by Phototropins

75%
Jedynak P., Malec P., Myśliwa-Kurdziel B., Turek E.
Acta Biologica Cracoviensia s. Botanica
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2013
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vol. 55
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issue 1
7
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The plant Nudix hydrolase family

75%
Kraszewska E.
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2008
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vol. 55
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issue 4
663-671
EN
Nudix hydrolases are a family of proteins defined by a conserved amino-acid sequence GX5-EX7REUXEEXGU, where U is a hydrophobic residue. These enzymes are widely distributed among all classes of organisms and catalyze, with varying degrees of substrate specificity, the hydrolysis of a variety of nucleoside diphosphate derivatives: nucleoside di- and triphosphates and their oxidized forms, dinucleoside polyphosphates, nucleotide sugars, NADH, coenzyme A and the mRNA cap. Nudix proteins are postulated to control the cellular concentration of these compounds. The genome of the model plant Arabidopsis thaliana contains 29 genes coding for putative Nudix hydrolases. Recently, several Arabidopsis Nudix genes have been cloned and their products characterized. This review summarizes current knowledge on these plant enzymes and discusses their possible cellular functions.
8
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Abscisic acid and blue light signaling pathways in chloroplast movements in Arabidopsis mesophyll

75%
Eckstein A., Krzeszowiec W., Banaś A., Janowiak F., Gabryś H.
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2016
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vol. 63
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issue 3
449-458
EN
Abscisic acid (ABA) and phototropins act antagonistically to control stomatal movements. Here, we investigated the role of ABA in phototropin-directed chloroplast movements in mesophyll cells of Arabidopsis thaliana. We analyzed the expression of phototropins at mRNA and protein level under the influence of ABA. PHOT1 mRNA level was decreased by ABA in the dark while it was insensitive to ABA in light. PHOT2 mRNA level was independent of the hormone treatment. The levels of phototropin proteins were down-regulated by ABA, both in darkness and light. No impact of exogenous ABA on amplitudes and kinetics of chloroplast movements was detected. Chloroplast responses in wild type Arabidopsis and three mutants, abi4, abi2 (abscisic acid insensitive4, 2) and aba1 (abscisic acid1), were measured to account for endogenous ABA signaling. The chloroplast responses were slightly reduced in abi2 and aba1 mutants in strong light. To further investigate the effect, abi2 and aba1 mutants were supplemented with exogenous ABA. In the aba1 mutant, the reaction was rescued but in abi2 it was unaffected. Our results show that ABA is not directly involved in phototropin-controlled chloroplast responses in mature leaves of Arabidopsis. However, the disturbance of ABA biosynthesis and signaling in mutants affects some elements of the chloroplast movement mechanism. In line with its role as a stress hormone, ABA appears to enhance plant sensitivity to light and promote the chloroplast avoidance response.
9
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The effect of bisphenol A on growth, pigment composition and photosystem II activity of Arabidopsis thaliana

75%
Rąpała M., Pluciński B., Jedynak P.
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2017
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vol. 64
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issue 3
407-413
EN
Bisphenol A (BPA) is a widely used chemical, that can potentially be toxic to plants. In this study we examined the toxicity of 5-50 mg/l of BPA on Arabidopsis thaliana. Additionally, the effects of 0.5-5 mg/l of BPA were examined after four weeks of development. BPA had no effect on the germination rate and the chlorophyll a/b ratio. The chlorophyll a and carotenoid content was significantly elevated in seedlings treated with 5 mg/l of BPA. In 4-week-old plants there was no change in the chlorophyll and carotenoid content and photosynthetic parameters (Fv/Fm, Fv/F0 and PI) were unaffected, which suggests no photoinhibition. No oxidative stress symptoms were observed. BPA significantly decreased leaf protein content. A low concentration of BPA seems to have no significant effect on A. thaliana flowering, but further investigation is needed. The results obtained indicate that a low concentration of BPA has no negative effect on the growth and development of A. thaliana.
10
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Arabidopsis thaliana Nudix hydrolase AtNUDT7 forms complexes with the regulatory RACK1A protein and Ggamma subunits of the signal transducing heterotrimeric G protein

75%
Olejnik K., Bucholc M., Anielska-Mazur A., Lipko A., Kujawa M., Modzelan M., Augustyn A., Kraszewska E.
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2011
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vol. 58
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issue 4
609-616
EN
Arabidopsis thaliana AtNUDT7 Nudix pyrophosphatase hydrolyzes NADH and ADP-ribose in vitro and is an important factor in the cellular response to diverse biotic and abiotic stresses. Several studies have shown that loss-of-function Atnudt7 mutant plants display many profound phenotypes. However the molecular mechanism of AtNUDT7 function remains elusive. To gain a better understanding of this hydrolase cellular role, proteins interacting with AtNUDT7 were identified. Using AtNUDT7 as a bait in an in vitro binding assay of proteins derived from cultured Arabidopsis cell extracts we identified the regulatory protein RACK1A as an AtNUDT7-interactor. RACK1A-AtNUDT7 interaction was confirmed in a yeast two-hybrid assay and in a pull-down assay and in Bimolecular Fluorescence Complementation (BiFC) analysis of the proteins transiently expressed in Arabidopsis protoplasts. However, no influence of RACK1A on AtNUDT7 hydrolase catalytic activity was observed. In vitro interaction between RACK1A and the AGG1 and AGG2 gamma subunits of the signal transducing heterotrimeric G protein was also detected and confirmed in BiFC assays. Moreover, association between AtNUDT7 and both AGG1 and AGG2 subunits was observed in Arabidopsis protoplasts, although binding of these proteins could not be detected in vitro. Based on the observed interactions we conclude that the AtNUDT7 Nudix hydrolase forms complexes in vitro and in vivo with regulatory proteins involved in signal transduction. Moreover, we provide the initial evidence that both signal transducing gamma subunits bind the regulatory RACK1A protein.
11
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Mutational analysis of the AtNUDT7 Nudix hydrolase from Arabidopsis thaliana reveals residues required for protein quarternary structure formation and activity

63%
Olejnik K., Płochocka D., Grynberg M., Goch G., Gruszecki W. I., Basińska T., Kraszewska E.
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issue 2
291-300
EN
Arabidopsis thaliana AtNUDT7, a homodimeric Nudix hydrolase active on ADP-ribose and NADH, exerts negative control on the major signaling complex involved in plant defense activation and programmed cell death. The structural and functional consequences of altering several amino-acid residues of the AtNUDT7 protein have been examined by site-directed mutagenesis, far-UV circular dichroism (CD), attenuated total reflection-Fourier transform infrared (ATR-FTIR) and photon correlation (PCS) spectroscopy, biochemical analysis and protein-protein interaction studies. Alanine substitutions of F73 and V168 disallowed dimer formation. Both the F73A- and V168A-mutated proteins displayed no observable enzymatic activity. Alanine substitution of the V69 residue did not significantly alter the enzyme activity and had no influence on dimer arrangement. The non-conserved V26 residue, used as a negative control, did not contribute to the enzyme quaternary structure or activity. Detailed biophysical characterization of the wild-type and mutant proteins indicates that the mutations do not considerably alter the secondary structure of the enzyme but they affect dimer assembly. In addition, mutating residues V69, F73 and V168 disrupted the binding of AtNUDT7 to the regulatory 14.3.3 protein. These are the first studies of the structure-function relationship of AtNUDT7, a Nudix hydrolase of important regulatory function.
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